1. Field of the Invention
The present invention relates to a film formation method and apparatus for a semiconductor process for forming a multi-layered film containing a carbon film, which is incorporated in, e.g., a multi-layered resist structure used as a mask for manufacturing semiconductor devices. The term “semiconductor process” used herein includes various kinds of processes which are performed to manufacture a semiconductor device or a structure having wiring layers, electrodes, and the like to be connected to a semiconductor device, on a target object, such as a semiconductor wafer or a glass substrate used for an FPD (Flat Panel Display), e.g., an LCD (Liquid Crystal Display), by forming semiconductor layers, insulating layers, and conductive layers in predetermined patterns on the target object.
2. Description of the Related Art
In the process of manufacturing semiconductor devices, a plasma etching process is performed by use a resist mask to form a circuit pattern. A photolithography technique is used to perform patterning of such a resist mask. For semiconductor devices in the generation with a CD of 45 nm, ArF resist is used to address miniaturization, but it is low in plasma resistance. In order to solve this problem, there is proposed a method in which a mask (having a multi-layered resist structure) is prepared by laminating an SiO2 film and a plasma resistant resist below ArF resist. However, for semiconductor devices in the generation with a CD of smaller than 45 nm, the film thickness of ArF resist needs to be as small as 200 nm. Where this ArF resist film thickness is used for plasma etching, an SiO2 film to be etched through the ArF resist and a resist film therebelow to be etched through the SiO2 film need to have a total thickness of smaller than 300 nm. In this case, however, such a mask cannot have a sufficient plasma resistance in light of the thickness of an etching target film, thereby deteriorating accuracy of etching. In light of this problem, an alternative film having a higher etching resistance is required in place of the resist film on the lower side. There is proposed a technique in which an amorphous carbon film is used as such an alternative film (U.S. Pat. No. 7,064,078 etc). Conventionally, studies are made to form an amorphous carbon film of this kind by single substrate CVD.
However, the single substrate CVD is high in initial cost and low in productivity. Further, since amorphous carbon can be easily oxidized and degraded, it is necessary to maintain the film quality of the amorphous carbon film when a subsequent film is formed on the amorphous carbon film.